1. Field of Invention
The present invention relates to a liquid crystal display and a method of manufacturing the same.
2. Description of the Prior Art
A liquid crystal display (LCD) typically comprises a plurality of thin film transistors (TFT) each having a pixel electrode, formed on a first substrate, a second substrate which includes a color filter and a common electrode, and a liquid crystal layer interposed between the first and second substrates. The LCD displays images by orienting liquid crystals to adjust the transmittance of light by applying voltage to the two substrates.
The TFT of such an LCD is typically formed as a semiconductor layer using amorphous silicon or polycrystalline silicon. A TFT manufactured with amorphous silicon has an advantage in that the uniformity of amorphous silicon film is superior and thus the characteristics of the TFTs are consistent. However, since an amorphous silicon TFT has low electric charge mobility, the response time of elements is long. Therefore, it is disadvantageous to use amorphous silicon TFTs in high-resolution display panel, or for driving elements of gate or data drivers which require a short response time.
However, since a TFT manufactured with polycrystalline silicon has high electric charge mobility, it is advantageous to use this type of TFT for a high-resolution LCD panel that requires short response time, as well as in peripheral driving circuits for the display panel.
In light of the development of digital convergence, there have been many attempts to embody additional functions for displaying images in an LCD. For example, it is desirable to add an automatic luminance adjusting function, a touch screen function, a scanning function and other features to an LCD. In order to achieve such additional functions, light receiving elements such as photo diodes need to be provided in an LCD panel. However, such light receiving elements are generally provided in a TFT substrate in which a circuit is easily configured.
However, since it is difficult to manufacture the TFT substrate together with photo diodes in the prior art, the aforementioned additional functions are implemented in such a manner that only circuits for connection are formed on TFT substrate and then separately manufactured photo diodes are mounted on the circuits of TFT substrate. Accordingly, there is a problem in that the manufacturing cost is increased due to the processes of manufacturing and mounting the photo diodes. A further disadvantage is that it is difficult to manufacture a thin LCD.